The Associated Press GENEVA — A leading conservation group uniting governments and civil society says all four known freshwater dolphin species are now threatened with extinction, after newly discovered information on the tucuxi in the Amazon river system showed it too is endangered. The finding from the International Union for Conservation of Nature comes as its latest “Red List” of threatened species, released Thursday, also showed that populations of the European bison — Europe’s largest land mammal — have improved, even as the list of extinct species overall has continued to expand. “The European bison and 25 other species recoveries documented in today’s IUCN Red List update demonstrate the power of conservation,” said Dr. Bruno Oberle,